In fall of 20 to 30 ft, the belayer has about 1300 ms from fall to peak. The point is the time to react and how to precisely synchronise his jump with the peak.

As USNavy says, you can define the peak as an even shorter period.

Try standing on a flat surface in belay stance and as quickly as possible, jump as high as possible. You might raise your CG by a couple of inches. That is, by a dynamic belay jump, you might be able to reduce the energy of the climber's fall by perhaps 1% or so ... if you time your jump precisely to the millisecond.

Belayers are better off forgetting about jumping to give an active dynamic belay, and locking off the rope correctly and focussing on not tripping or hitting the wall if on an indirect belay.

I don´t jump, don´t recommend it and don´t expect anyone to do it. Nor would I teach it. That was USNavy´s idea and how he achieves this I have no idea, he´s probably younger, more athletic and has better reactions than me. Since I weigh over 200lbs my belayers generally give me a dynamic belay whether they want to or not, when I´m belaying I try to give a dynamic belay if required by relaxing towards the tension of the rope as shown in the Petzl cartoon. Mostly I don´t bother since the bottom of the cliffs where I mostly climb are an upward slope which makes things awkward and anyway I´d probably spill my coffee by moving fast.

The amount of movement required is very low to reduce the peak force, six inches or a foot at the belayer end makes a huge difference and probably wants to be given at an early stage in the arrest of the fall. If you timed it to coincide with the absolute peak force then you are far too late as there is a time delay through the whole process.

If I need to give a soft catch to reduce the swing into the rock then it´s a whole different concept and process (and belay device generally).

... Certainly amongst MY local TRAD community dynamic belays are never emphasised.

And amongst my local sport community, I've never seen anyone do a dynamic belay.

Either you don't have a very sporty "local sport community" or you are not paying attention. Observe sport climbers at any major sport area..think the Red, the New, Obed, Rifle, Rumney (sorry, US-centric I know, but those are the areas that I am familiar with)...and you will observe prolific dynamic belaying in practice. Even here in NC, with very few bolts, I see it all the time.

THe point is much less about minimizing peak load than it is about reducing the slam into the wall produced by the pendulum effect. IT's not that hard. You don't have to really "jump" unless you really outweigh your climber. GIve into the pull of the fall and allow yourself to be pulled up. I routinely end up hanging 10 or more ft up when my climber falls.

Unless, of course, there is something to hit below the climber..then that take precedence. Keep the climber from hitting dangerous things 1st, soften the catch 2nd. IF I'm slab climbing, usually with big runnouts, then shortening the fall gets bumped up in priority.

... Mostly I don´t bother since the bottom of the cliffs where I mostly climb are an upward slope which makes things awkward and anyway I´d probably spill my coffee by moving fast...

I'd say that matches the scene where I climb. Don't forget the rubble and talus I'm standing on, too.

But the hard part is, I don't have a load cell. If I did, we could set-up a "quick and dirty" point at the top anchor and record from there. Although I don't know anybody who would volunteer to leave his laptop perched up there, on a ledge (if there is a ledge). And then jump off, for a ff1 fall! With a belayer who'd jump, just before the faller hits the ground? They'd both be crazy!

I agree with JimTitt that a "jump" is not practical and not even practicable (hey! there's a good word!). So I obey my own rule: "Never let go of the brake strand."

And once again, I make the effort to remind everyone here, that the OP's set-up measures a "static anchor", and not a "dynamic belay"! !! !!!

... Certainly amongst MY local TRAD community dynamic belays are never emphasised.

And amongst my local sport community, I've never seen anyone do a dynamic belay.

Either you don't have a very sporty "local sport community" or you are not paying attention. Observe sport climbers at any major sport area..think the Red, the New, Obed, Rifle, Rumney (sorry, US-centric I know, but those are the areas that I am familiar with)...and you will observe prolific dynamic belaying in practice. Even here in NC, with very few bolts, I see it all the time.

THe point is much less about minimizing peak load than it is about reducing the slam into the wall produced by the pendulum effect. IT's not that hard. You don't have to really "jump" unless you really outweigh your climber. GIve into the pull of the fall and allow yourself to be pulled up. I routinely end up hanging 10 or more ft up when my climber falls.

Unless, of course, there is something to hit below the climber..then that take precedence. Keep the climber from hitting dangerous things 1st, soften the catch 2nd. IF I'm slab climbing, usually with big runnouts, then shortening the fall gets bumped up in priority.

No! You are not paying attention!

1. The OP is about measuring a static anchor, not the technique of dynamic belay.

2. I don't live near any of those places. I live near the Canadian Rockies. You know, up there in the great white frozen wasteland?

Anyway it's Sunday now and I'm loading my gear into the car. In a couple of hours I'll be snow-shoeing and scrambling a ridge on Mount Baldy. Tame enough, but it provides plenty of adventure. The rocks aren't too high, but all the features are covered with snow. It's sheltered by forest, so the venue is very pleasant. I'll try to get some snapshots of the static anchors I set up.

And I believe there has been other good research to support this. Dynamic belaying was found produce only very minor reductions in peak load.

Thanks patto.

I've done some experiments to support this. The maximum effect of a dynamic belay is the instant the belayer's feet leave the ground. The fastest time I recorded was 800 millisecs from the instant a climber yells or is seen to fall, to the belayer's feet leaving the ground in an active hop. 200 ms later, the belayer is headed for the ground again (unless he is yanked upwards of course). Another 200 ms and the belayer is adding to the impact on the climber.

A "typical" free fall of 20 feet takes 1200 ms. In the next 200 ms, the climber falls another 8 feet. For a dynamic belay to work, the belayer has 400ms to calculate the amount of slack, how far the climber will fall and hence exactly when to jump.

To put things into perspective, "the blink of an eye" is 300 to 400 milliseconds. That is, the belayer must literally do the above calculations in the blink of an eye. If he's a blink of an eye out, he adds to the impact on the climber.

In summary, dynamic belaying is a myth. It might make you feel good in that you fool yourself into thinking you are helping but it's useless.

And I believe there has been other good research to support this. Dynamic belaying was found produce only very minor reductions in peak load.

Thanks patto.

I've done some experiments to support this. The maximum effect of a dynamic belay is the instant the belayer's feet leave the ground. The fastest time I recorded was 800 millisecs from the instant a climber yells or is seen to fall, to the belayer's feet leaving the ground in an active hop. 200 ms later, the belayer is headed for the ground again (unless he is yanked upwards of course). Another 200 ms and the belayer is adding to the impact on the climber.

A "typical" free fall of 20 feet takes 1200 ms. In the next 200 ms, the climber falls another 8 feet. For a dynamic belay to work, the belayer has 400ms to calculate the amount of slack, how far the climber will fall and hence exactly when to jump.

Sorry, but you are completely full of shit. The belayer simply jumps as soon as he feels tension in the rope. It really is that simple.

And I believe there has been other good research to support this. Dynamic belaying was found produce only very minor reductions in peak load.

Thanks patto.

I've done some experiments to support this. The maximum effect of a dynamic belay is the instant the belayer's feet leave the ground. The fastest time I recorded was 800 millisecs from the instant a climber yells or is seen to fall, to the belayer's feet leaving the ground in an active hop. 200 ms later, the belayer is headed for the ground again (unless he is yanked upwards of course). Another 200 ms and the belayer is adding to the impact on the climber.

A "typical" free fall of 20 feet takes 1200 ms. In the next 200 ms, the climber falls another 8 feet. For a dynamic belay to work, the belayer has 400ms to calculate the amount of slack, how far the climber will fall and hence exactly when to jump.

To put things into perspective, "the blink of an eye" is 300 to 400 milliseconds. That is, the belayer must literally do the above calculations in the blink of an eye. If he's a blink of an eye out, he adds to the impact on the climber.

In summary, dynamic belaying is a myth. It might make you feel good in that you fool yourself into thinking you are helping but it's useless.

Seriously. STFU with your theory. At 180lbs, belaying girls on a regular basis means dynamic belays are a necessity. Otherwise quite the slam results. I would estimate 99% of the hundreds of falls I've caught I've timed the jump correctly. You have no idea WTF you are talking about.

... Certainly amongst MY local TRAD community dynamic belays are never emphasised.

And amongst my local sport community, I've never seen anyone do a dynamic belay.

Either you don't have a very sporty "local sport community" or you are not paying attention. Observe sport climbers at any major sport area..think the Red, the New, Obed, Rifle, Rumney (sorry, US-centric I know, but those are the areas that I am familiar with)...and you will observe prolific dynamic belaying in practice. Even here in NC, with very few bolts, I see it all the time.

THe point is much less about minimizing peak load than it is about reducing the slam into the wall produced by the pendulum effect. IT's not that hard. You don't have to really "jump" unless you really outweigh your climber. GIve into the pull of the fall and allow yourself to be pulled up. I routinely end up hanging 10 or more ft up when my climber falls.

Unless, of course, there is something to hit below the climber..then that take precedence. Keep the climber from hitting dangerous things 1st, soften the catch 2nd. IF I'm slab climbing, usually with big runnouts, then shortening the fall gets bumped up in priority.

No! You are not paying attention!

1. The OP is about measuring a static anchor, not the technique of dynamic belay.

2. I don't live near any of those places. I live near the Canadian Rockies. You know, up there in the great white frozen wasteland?

Anyway it's Sunday now and I'm loading my gear into the car. In a couple of hours I'll be snow-shoeing and scrambling a ridge on Mount Baldy. Tame enough, but it provides plenty of adventure. The rocks aren't too high, but all the features are covered with snow. It's sheltered by forest, so the venue is very pleasant. I'll try to get some snapshots of the static anchors I set up.

I wasn't addressing the OP, genius, I was addressing you. If you can read the highlighted and underlined sentence above, YOU are talking about a dynamic belay and how you've "never seen anyone do a dynamic belay in your local sport climbing community". And my original statement stands. Either you are not paying attention to your local sport climbing community or you don't have one. Dynamic belays are commonplace at every sport climbing crag I've ever seen and they are effective. Period.

... I wasn't addressing the OP, genius, I was addressing you. If you can read the highlighted and underlined sentence above, YOU are talking about a dynamic belay and how you've "never seen anyone do a dynamic belay in your local sport climbing community". And my original statement stands. Either you are not paying attention to your local sport climbing community or you don't have one. Dynamic belays are commonplace at every sport climbing crag I've ever seen and they are effective. Period.

Sorry, but you are completely full of shit. The belayer simply jumps as soon as he feels tension in the rope. It really is that simple.

Jay

Pointing out that traditional view are nonsense is like Galileo pointing out the Earth revolves around the sun.

Jt, if you jump as soon as you feel the tension in the rope, your effort is almost a second too late. You will be fooled into thinking you have done something useful because you will be lifted off the ground by the falling climber. If you do nothing, you will be lifted off the ground just the same.

I'm sure all those people dynamic belaying will keep doing it because it feels good to think they might be doing something useful. At least it does no harm. The smarter folk will just smile knowingly.

Sorry, but you are completely full of shit. The belayer simply jumps as soon as he feels tension in the rope. It really is that simple.

Jay

Pointing out that traditional view are nonsense is like Galileo pointing out the Earth revolves around the sun.

Jt, if you jump as soon as you feel the tension in the rope, your effort is almost a second too late. You will be fooled into thinking you have done something useful because you will be lifted off the ground by the falling climber.

You're still arguing theory in the face of overwhelming contrary evidence. As a 135-climber I can assure you that I can feel the difference between when my heavier partners do and do not dynamically belay.

In reply to:

If you do nothing, you will be lifted off the ground just the same.

That's patently false when the belayer outweighs the climber or there is substantial friction in the system.

Sorry, but you are completely full of shit. The belayer simply jumps as soon as he feels tension in the rope. It really is that simple.

Jay

Pointing out that traditional view are nonsense is like Galileo pointing out the Earth revolves around the sun.

Jt, if you jump as soon as you feel the tension in the rope, your effort is almost a second too late. You will be fooled into thinking you have done something useful because you will be lifted off the ground by the falling climber. If you do nothing, you will be lifted off the ground just the same.

I'm sure all those people dynamic belaying will keep doing it because it feels good to think they might be doing something useful. At least it does no harm. The smarter folk will just smile knowingly.

When my 210 lb partner falls I get lifted off the ground if I don't jump. When my 120 lb partner falls I remain exactly where I stand if I don't jump. I assure you, their experience during the fall is very different.

As a 155 lb climber who has been belayed by those who weight significantly more and less than I do, I can attest to this fact. A well timed jump makes a tremendous difference.

And I believe there has been other good research to support this. Dynamic belaying was found produce only very minor reductions in peak load.

Maybe research done by high school kids. Any reputable research done by anyone that knows what they are doing will show the opposite of what you claim, except in extremely low fall factor scenarios.

Syd wrote:

That is, by a dynamic belay jump, you might be able to reduce the energy of the climber's fall by perhaps 1% or so .

That is completely incorrect. You are overthinking it. Dynamic belaying is not as much of a precision art as you believe it is. Close is good enough. You dont need to time things to the millisecond.

Syd wrote:

patto wrote:

I completely agree with this.

And I believe there has been other good research to support this. Dynamic belaying was found produce only very minor reductions in peak load.

Thanks patto.

I've done some experiments to support this. The maximum effect of a dynamic belay is the instant the belayer's feet leave the ground. The fastest time I recorded was 800 millisecs from the instant a climber yells or is seen to fall, to the belayer's feet leaving the ground in an active hop. 200 ms later, the belayer is headed for the ground again (unless he is yanked upwards of course). Another 200 ms and the belayer is adding to the impact on the climber.

A "typical" free fall of 20 feet takes 1200 ms. In the next 200 ms, the climber falls another 8 feet. For a dynamic belay to work, the belayer has 400ms to calculate the amount of slack, how far the climber will fall and hence exactly when to jump.

To put things into perspective, "the blink of an eye" is 300 to 400 milliseconds. That is, the belayer must literally do the above calculations in the blink of an eye. If he's a blink of an eye out, he adds to the impact on the climber.

In summary, dynamic belaying is a myth. It might make you feel good in that you fool yourself into thinking you are helping but it's useless.

Allow me to show you what actually happens when you give a dynamic belay and when you dont. I tested this at my local crag using standard belaying techniques found in use by any experienced sport climber.

Those graphs show quite clearly that the difference between dynamic and a simple belay is negligible.

Also all the comment regarding sport climbing and stopping the pendulum effect miss the point. A dynamic belay is not the best solution to avoiding a pendulum! The best solution is allowing more slack!

Those graphs show quite clearly that the difference between dynamic and a simple belay is negligible.

Also all the comment regarding sport climbing and stopping the pendulum effect miss the point. A dynamic belay is not the best solution to avoiding a pendulum! The best solution is allowing more slack!

An 18% reduction in peak is negligible?

In regards to swinging into the wall. It isn't about peak force but rather horizontal velocity that matters. A pretty good discussion from a while back shows the merits of a dynamic belay(as well as initial slack). http://www.rockclimbing.com/..._reply;so=ASC;mh=25;"Theory" shows ~40-60% reduction in horizontal energy

Also all the comment regarding sport climbing and stopping the pendulum effect miss the point. A dynamic belay is not the best solution to avoiding a pendulum! The best solution is allowing more slack!

First of all, just to clear-up a few myths, the following is not dynamic belaying:

1) Dynamic belaying involves giving lots of slack - FALSE!

The more slack there is in the system, the further the climber will fall before the rope can start to do its job and the more force will need to be absorbed. Unless there is an obvious hazard that you need to steer the falling climber away from, give only enough slack to allow freedom of movement.

We also stress that dynamic belaying does not mean keeping 3-4 m of slack in the climber’s side of the rope: this does not reduce the force of a fall. In addition, in the case where the climber has not gained enough height, it increases the risk of a ground fall.

First of all, just to clear-up a few myths, the following is not dynamic belaying

So instead of clearing up myths you continue to mix up and confuse the issues of reducing pendulums and reducing impact force!

More slack will increase the impact forces, nobody is arguing otherwise. More slack will significantly reduce the pendulum effect. A dynamic belay will normally slightly reduce impact forces. A dynamic belay will slighty reduce the pendulum effect.

First of all, just to clear-up a few myths, the following is not dynamic belaying

So instead of clearing up myths you continue to mix up and confuse the issues of reducing pendulums and reducing impact force!

More slack will increase the impact forces, nobody is arguing otherwise. More slack will significantly reduce the pendulum effect. A dynamic belay will normally slightly reduce impact forces. A dynamic belay will slighty reduce the pendulum effect.

are you whinning about UKclimbing confusing stuff for ya

how many sport whippers do you catch in a day ... 15+ footers? ... a decent sport climber at their limit will easily take 5-10 or more in a day ... and catch that many ...

the effect of a dynamic belay is often more than "slight" ... as anyone who sport climbs a decent amount will know friends that have busted ankles from hard catches

im a wussy climber and i climb sport at my limit indoor and outdoor 2-3 times a week ... 5-10 whippers a day ... basically 1000+ not so short falls a year .... and there are many that take much more than that

if you climbed and fell constantly on sport, all it takes is one hard catch where you tweak your ankle to see what works ... and what doesnt

First of all, just to clear-up a few myths, the following is not dynamic belaying

So instead of clearing up myths you continue to mix up and confuse the issues of reducing pendulums and reducing impact force!

More slack will increase the impact forces, nobody is arguing otherwise. Alot More slack will significantly reduce the pendulum effect. A dynamic belay will normally slightly reduce impact forces. A dynamic belay will slightysignificantly reduce the pendulum effect.

The difference is that using slack to decrease the pendulum effect comes at a cost of much farther fall to achieve the same affects as dynamic belaying. You still have the higher overall impact forces as well. Dynamic belaying results in all the benefits and no drawbacks.

So a foot of dynamic jumping is so much better than a foot of slack in reducing the pendulum!

patto wrote:

So a foot of dynamic jumping is so much better than a foot of slack in reducing the pendulum!

Yes, by a long shot.

patto wrote:

I'm not faulting dynamic belays, I'm just saying that they have massively overstated benefits. If you want a softer catch then buy a BEAL rope!

It is far better to use a stretchy rope to absorb energy and reduce a pendulum than doing a little jump.

You are still missing the point.The impact force rating of the rope has a marginal effect on the pendulum effect. The dynamic belay changes the arc of the pendulum significantly enough to decrease the horizontal for by~40%+. This is best illustrated in Blondgecko's image found the thread I posted That change in trajectory is what saves ankles, not the lower peak impact force. Albeit that is somewhat idealized.

I still don't get why you are arguing this. Sport climbers are literally utilizing this hundreds to thousands of times a day to decrease the pendulum into the wall. It isn't hard to learn, and it can be used in conjuction with slack and low impact ropes to further reduce slams into the wall.

So a foot of dynamic jumping is so much better than a foot of slack in reducing the pendulum! Crazy Laugh

I'm not faulting dynamic belays, I'm just saying that they have massively overstated benefits. If you want a softer catch then buy a BEAL rope!

It is far better to use a stretchy rope to absorb energy and reduce a pendulum than doing a little jump.

If you introduce slack, the fall distance will be greater, the impact force will be greater, but the pendulum effect will be reduced. A well done dynamic belay will have all of the pluses (reduced pendulum effect) and still reduce impact force. And it is not that hard, it get's done all the time. Being a lighter climber, I can definitely feel when my belayer is soft or not.

The other thing that you're missing that putting slack in the rope gives you no option but to increase the fall distance. If you do not (arbitrarily) introduce slack you can adjust your belay to the situation. If you need to shorten the fall because of a ledge, you do not give the dynamic belay. If you had slack in the system, this is not an option. If there is nothing to hit, you can belay dynamically with all of the benefits as if you had put slack in the system, without having to yard rope in an out to adjust for every changing situation.

If you only get pulled up a foot in your dynamic belay...you are definitely doing it wrong. I routinely allow myself to be pulled up a good 10 ft. So you'd rather I just leave 10 ft of slack in the rope? Let's say my climber has 10 ft of slack in the line and decides s/he quickly wants to step down and hang...if I were prepared for any type of belay, be it dynamic or otherwise (eg no slack!), all I'd have to do is essentially sit down and take. With your 10 ft of slack out I'd have to take all that rope in and then take their weight. No thanks.